| ??? 07/14/10 18:15 Read: times |
#177291 - Shielding Responding to: ???'s previous message |
Daniel said:
Sometimes, you can see a closed loop of cooper around the transformer. The idea of this is to provide a "trap" for the disperse flux and to reduce the parasite induction in conductors outside the transformer (in audio equipment, for example). The magnetic shielding of 50Hz by copper is entirely zero, unless you take centimeters thick copper. No, this copper only shields the electric fields from the windings. 1mm (unalloyed!) iron foil allows about 5...10dB of shielding against 50Hz magnetic fields. About 10mm of copper or aluminium equals this. Only MU-metal can considerably shield against 50Hz magnetic fields, but only rather low intensities, otherwise saturation occurs. So, you can easily shield an audio transformer against (rather low) magnetic stray fields, but it's very hard to successfully shield a mains transformer. You need to separate the magnetic shield from the mains transformer, so that no saturation occurs... Raghunathan, an isolation transformer provides isolation against electric shock. In the earlier days, when providing isolation by plastic foils wasn't very reliable, a metal shield between primary and secondary winding was added an connected to protection earth. Today, you can provide isolation against many thousands of volts even without any metal shields. This entirely depends on the skills of your manufacturer of transformer. Or is there another reason to have a shield between primary and secondary winding? Kai Klaas |
| Topic | Author | Date |
| (Simple) Isolation transformer | 01/01/70 00:00 | |
| All depends on what you want in terms of specs | 01/01/70 00:00 | |
| Some more inputs | 01/01/70 00:00 | |
| Induction doesn't work with low frequencies or DC | 01/01/70 00:00 | |
| E-cores | 01/01/70 00:00 | |
| U core | 01/01/70 00:00 | |
| What I would do... | 01/01/70 00:00 | |
| Shielding | 01/01/70 00:00 | |
| The use of shield... | 01/01/70 00:00 | |
| Side-by-side windings exists on E cores | 01/01/70 00:00 | |
| is 4kV enough | 01/01/70 00:00 | |
| Transformer Design | 01/01/70 00:00 | |
Why 415V to 230V? | 01/01/70 00:00 |